Method and apparatus for the production of seismic shocks

Abstract

A releasable heavy mass is provided which is capable of producing by impact with the ground a shock which can be used in seismic prospecting. This mass is characterized by the fact that it comprises very many individual heavy elements connected together in a way loose enough to allow deformation of the mass without loss of cohesion on impact, and in that its base is of considerable area relative to the surface of the whole mass and is maintained substantially plane at least after release and up to impact. The mass is, in seismic prospecting, released from a helicopter.

I claim: 
     
       1. A method for producing shocks in the ground, comprising the step of releasing a mass for free fall from an aircraft from a height of between about 5 and 100 meters, said mass comprising a multiplicity of individual heavy elements connected together, and a base of large relative surface, said mass on impact with the ground deforming without losing cohesion, said release step including the steps of: maintaining said base substantially plane by providing means for stiffening the base; and maintaining the base substantially horizontal at least after release and up to impact. 
     
     
       2. A releasably heavy mass capable of being released from an aircraft from a height of between about 5 and 100 meters and of producing by impact with the ground a shock exploitable in seismic prospecting, said mass comprising: a multiplicity of individual heavy elements connected together in a way loose enough to allow deformation of the mass without loss of cohesion on impact, the mass having a lower portion comprising a base portion; and   base stiffening means for stiffening said base portion of the mass and biasing at least the lower of said elements towards a substantially horizontal base plane at least after said release and up to said impact.   
     
     
       3. A releasable heavy mass capable of being released from an aircraft from a height of between about 5 and 100 meters and of producing by impact with the ground a shock exploitable in seismic prospecting, said mass comprising: a multiplicity of individual heavy elements connected together in a way loose enough to allow deformation of the mass without loss of cohesion on impact; and   base stiffening means for biasing at least the lower of said elements towards a substantially horizontal base plane at least after said release and up to said impact,   wherein said heavy elements comprise shot surrounded by at least one flexible and resistant casing and said base stiffening means comprises at least one framework with a substantially planar base.